|Lindqvist et al. (1988)a||-||-||-||-||-|
|Omont et al. (1993)b||-||-||-||-||-||-|
|Bujarrabal et al. (1994)c||-||-|
|Kim et al. (2010)d (``case A'')|
|Kim et al. (2010)d (``case B'')|
|et al. (2003)||-||-||-||-||-||-||-|
|Schöier et al. (2007a)f||-||-||-||-||-||-||-|
|Duari et al. (1999)h||-||-|
|Willacy & Millar (1997)j||-|
the first part of the table, observational results are listed based on
the assumption of optically thin emission and a population distribution
which is thermalized at one excitation temperature. The second part
gives observational results based on a non-LTE radiative transfer
analysis. Theoretical predictions for either the inner envelope (Cherchneff
2006; Duari et al. 1999)
or outer envelope (Willacy
& Millar 1997) fractional abundances are given in the
All fractional abundances are given relative to the total H-content. In cases where values found in literature were given relative to H2, they were re-scaled relative to the total H-content by assuming that all hydrogen is in its molecular form H2.
References. (a) No information on used distance and mass-loss rate; (b) distance is 270 pc, = 4.5 10-6 /yr; (c) distance is 270 pc, = 4.5 10-6 /yr; (d) distance is 250 pc, assumed of 4.7 10-6 /yr, LTE is assumed, ``case B'' represents a solution with a larger outer radius than ``case A''; (e) in Gaussian distribution for SiO is 2.5 1016 cm, distance is 250 pc and = 3 10-5 /yr; (f) in Gaussian distribution for SiS, distance is 260 pc and = 1 10-5 /yr. For 2-component model: is 5.5 10-6 and taken constant out to 1.0 1015 cm and the lower abundance Gaussian component has f0 of 5.0 10-9 and of 1.6 1016 cm. Using one (Gaussian) component distribution, f0 is 5 10-8 and is 1.6 1016 cm; (g) only value at 5 is given; (h) predicted values at 2.2 in the envelope for IK Tau; (i) predicted values at 2 in the envelope for TX Cam; (j) predicted peak fractional abundances in the outer envelope.
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